中国古人发现杠杆原理的年代

When Lever Principle Was Discovered in Ancient China

杠杆原理是古代各类衡器工作时必须遵循的基本原理，在传统计量发展过程中具有重要作用。杠杆原理被人们掌握的时间，不晚于不等臂天平出现的年代。不等臂天平的出现，其前提条件是制造者对杠杆原理的掌握。在中国，先秦典籍《墨经》最早从理论上叙述了不等臂天平的工作特点；而在燕昭王时，人们亦曾试图利用杠杆方式称量巨豕之重；现存出土文物中，亦有可以作为不等臂衡秤使用的战国铜衡。综合这些因素，可以认为至迟在战国时代，我国先民已经掌握了杠杆原理，这在时间上并不晚于西方。

Lever principle is a basic principle that all kinds of weighing apparatus in ancient time must abide by. It had played an important role in the developing process of traditional metrology. The time when it was known by ancient people cannot be later than that when lever scale with different beams was used. The essential prerequisite for using lever scale is that its maker knew the principle well. The pre-Qin book Mojing is the first in ancient China that described the working characteristic of lever scale theoretically. During the period of Zhao King of the Yan State,people had ever tried to weigh a huge pig in lever. Moreover,there are copper lever scales of the Warring States period (475- 211 BC)existed in unearthed cultural relics today. Considering those factors mentioned above,we might say that the time when lever principle was discovered in ancient China was no later than the Warring States period, which is nearly at the same time with Western countries.